The present invention relates to a method for cutting a web feeding tail, in which method
the web feeding tail is detached from the roll,
the web feeding tail is guided against the cutting device,
the web feeding tail is tension ed for cutting,
the web feeding tail is cut with a single work stroke of the blade of the cutting device, without a counter-blade, and
the cut web feeding tail is guided forwards from the cutting device, in the desired direction to the following web feeding device.
The invention also relates to a corresponding cutting device.
At certain points, the transfer of the web from one section of a paper machine to the next is started using a narrow web feeding tail. The web feeding tail, which generally has a width of less than 500 mm, is cut from the edge of the full-width paper web. After web feeding, once the web feeding tail is moving over the correct route, the web feeding tail is finally broadened to the full width of the web.
Usually, the web feeding tail is cut before beginning the actual feeding of the web. In known devices, various jets of air are used both to cut the web feeding tail and to direct it. Finish patent number 82101 discloses a cutting device, in which there is also a blade without a counter-blade for cutting the web feeding tail. In a cutting device according to this patent, two blasts of air, by means of which the web feeding tail can be guided in the desired direction. In the case of thinner grades of paper, the web feeding tail breaks already from the effect of the second blast of air. For thicker paper grades, the device also has a blade arranged between the blower pipes, which rotates to cut through the web feeding tail, without a counter-blade.
When cutting using an air blast, the exact point and time of the cut in the web feeding tail are imprecise. In addition, the cut surface becomes uneven, which makes it difficult to guide the web feeding tail. The ragged end may also result in the unintentional breaking or crumpling of the web feeding tail at a later stage. When applying the device of the aforesaid patent, a fold also forms in the web feeding tail, which it may not be possible to straighten in time. The web feeding tail may then fold twice, in which case the tail after the fold will interfere greatly with web feeding. In addition, the rotating blade creates a lateral movement in the web feeding tail, which further interferes with the control of the end. Even if the web feeding tail is relatively narrow, it is still able to move forward during cutting. Thus, the cut surface acquires a slant. This problem appears especially in modern, high-speed machines.
The typical speed of the web feeding tail in web feeding is 20-30 m/s, in some cases, as much as 33-38 m/s. At the same time, it is difficult to regulate the forces of the air blasts of the cutting device, so that the cutting of the web feeding tail and even the success of the web feeding itself are uncertain. This increases the total time of the web feeding and the amount of waste paper. The installation of the cutting device disclosed also requires a great deal of space.
The invention is intended to create a method of cutting a web feeding tail, by means of which the formation of tails and other folds in the web feeding tail can be avoided, and which is simpler and more reliable than previously. The invention is also intended to create a web feeding tail cutting device, which is fast, precise, and reliable, and which can be applied to all grades of paper. A method for cutting a web feeding tail, in which method the web feeding tail is detached from the roll, the web feeding tail is guided against the cutting device, the web feeding tail is tension ed for cutting, the web feeding tail is cut with a single working stroke of the blade of the cutting device, without a counter-blade, and the cut web feeding tail is guided forwards, from the cutting device, in the desired direction to the next web feeding device, wherein the cutting device is located on the opposite side of the web feeding tail to the aforesaid following web feeding device, the web feeding tail is tension ed against a guide surface arranged in the cutting device, at the end of which guide surface, in the direction of travel of the web feeding tail, there is an edge, the blade is arranged essentially after the edge, in the aforesaid direction of travel, before cutting, the aforesaid following web feeding device is moved essentially to the location of the blade and into an essentially transverse position in relation to the web feeding tail, the web feeding tail is cut with a single rapid stroke of the blade over the entire width of the web feeding tail, when, at the same time, the cut end of the web feeding tail is guided from the blade to the aforesaid following web feeding device.
After the cutting of the web feeding tail, the blade may be left at the end of its work stroke to form a protrusion to guide the cut end of the web feeding tail to the following web feeding device. After the work stroke of the blade, a blast of air may be directed from the cutting device in the desired direction.
A cutting device for a web feeding tail, which is intended to cut the web feeding tail and then to guide the cut web feeding tail in the desired direction, and which cutting device includes devices for detaching the web feeding tail from the roll, first web feeding devices for guiding the web feeding tail against the cutting device and for tensioning the web feeding tail for cutting, a blade connected to an operating device for cutting the web feeding tail with a single working stroke, without a counter-blade, and second web feeding devices for guiding the cut web feeding tail guided forwards, from the cutting device, in the desired direction, wherein the second web feeding device includes a guide plate, on the opposite side of the web feeding tail to which the cutting device is arranged, the guide plate is arranged to be moved essentially to the location of the blade at a distance from the web feeding tail, so that the web feeding tail is arranged to travel between the cutting device and the front of the guide plate, the aforesaid first web feeding devices are arranged to form a guide surface, against which the web feeding tail is arranged to be tension ed for cutting, an edge, which ends in the direction of travel of the web feeding tail, immediately after which the blade is located, and the work stroke path of the blade, which is arranged to operate in pulses, is arranged essentially according to the desired direction of the web feeding tail.
An auxiliary blast of air, may be arranged before the blade essentially parallel to the guide plate. The guide plate may be supported rotatably on an articulated joint, in such a way that the front of the guide plate is close to the cutting device.
In the operating position, the distance of the front of the guide plate from the cutting device is 20-100 mm and preferably 45-75 mm.
The devices for detaching the web feeding tail from the roll, and the cutting device may be arranged as a single entity, which entity is fitted rotatably in relation to bearer axles.
The first web feeding devices may include a blower plate, between the parts of which the blade is arranged to cut the web feeding tail. The part of the blower plate after the blade may be supported on an articulated joint, so that the aforesaid part can be turned from the rest position into the operating position.
In the method according to the invention, the blade of the cutting device is used to guide the web feeding tail, as well as to cut it. In addition, the blade is arranged to cut the web feeding tail simultaneously over its entire width, so that the cut is rapid and the cut even is even. The tail is guided immediately from the cutting device to the following web feeding device. Thus, the web feeding tail being guided remains only a single thickness and detrimental folds and tails are not formed. In addition, during cutting the web feeding tail is always under control, so that web feeding seldom fails. There are also clear stages in web feeding and the cutting of the web feeding tail, which increases the likelihood of success. In addition, the device requires little installation space and contains few moving parts.